This invention relates to an automatic pencil apparatus for an automated drafting system.
Recently, some companies have developed the automated drafting system, in which a drafting head driven by the linear pulse motor or a like runs on the drafting paper so as to plot drawings and symbols. Such a drafting system is currently available for practical use.
For these automated drafting systems, drawings were frequently desired to be drawn using pencil lead as the drawing medium to provide erasable drawings. However, there has not heretofore been developed a suitable mechanism which gives the optimum pressure on the lead so as to plot smoothly on the paper and enables the lead to be removed at the end of drawing lines, and which can slide the leads succesively in response to the abrasion of lead.
This invention aims to solve the above problems by providing an apparatus having a gripping mechanism which holds the lead and lifts it up to a predetermined height, the gripper driving mechanism which actuates the gripper to hold and lift the lead and to release the lead, and a pressing mechanism which gives constant downward pressure on the lead. In the apparatus of the present invention, when the gripping mechanism releases the lead, the tip of the lead touches the paper under a predetermined pressure determined by the pressing mechanism, independently of the abrasion of lead. On the other hand, when the gripping mechanism holds and lifts up the lead, the apparatus according to the present invention enables the lead to be removed from the paper.